Posted by James Briggs on August 13, 2004
Our Archive suggest that the expression comes from the US Weather Bureau's classification oif clouds. That may be, but it may be only part of the truth. Here's what was printed in today's Q&A cloumn in the Times, in response for an origin for the phrase. Incidentally, I'm ingnoring the Archioval Bhuddist possible origin for the moment.
Probably the first efforts at properly classifying clouds was at the beginning of the 19th century by Jean Baptiste de Lamarck, who classified them in simple terms along Linnaean lines. Then, a Quaker businessman, Luke Howard (1772-1864), classified clouds into types such as stratus, cumulus and cirrus. Howard's system was expanded and developed into the International Cloud Atlas.
An abridged version of the atlas came out in 1896 and classified ten types of cloud. Number 9 was the white, fluffy, comfy-looking cumulo-nimbus. Hence to be "on cloud nine" came to symbolise floating free on a downy, white cushion, presumably without a care in the world.
Robert Steele, Doune, Perthshire